Bioelectrical stimulus leads in general and pain management leads in particular have proven to be an important addition to mankind's set of tools for addressing bodily malfunction. Unfortunately, heretofore these leads have been made one at a time in a fairly expensive operation that included the use of a lathe to turn a set of insulated wires together about a mandrel and then the application of heat and pressure to fuse the insulation of the wires together. Additionally, at least in part because the lathe wrapping process results in a lead body having a varying outer diameter and insulation thickness, the previous method has encountered a fairly high defect rate, driving up the price for correctly manufactured leads. Later operations, in which electrodes are created in the lead body require a uniform outer diameter and insulation thickness to avoid frequent accidental damage to the lead bodies, due to an uncertain amount of insulation removal needed to reach the underlying wire. This uncertainty has made it impractical to automate the process.
A separate problem that occurs when helically winding wires about a mandrel is that of residual stress being imparted to the wires. In the prior art, two basic options are available for this kind of wire wrapping. In both options, a set of payout carriers are mounted on a turn table having a central aperture through which the core being wrapped is advanced. The turntable is rotated about this mandrel and the payout carriers let out wire, which helically wraps the mandrel. In a first option, known as a planetary system, the payout carriers are maintained in a stationary orientation relative to an absolute coordinate system. In the second option, the payout carriers are maintained in a stationary orientation relative to the turntable (“stationary re turntable” case). For each option, however, residual stress is imparted to wires as they are wrapped because the ideal amount of payout carrier rotation falls in between the planetary case and the stationary re turntable case.
Also, some references show a lead being made by taking a group of insulated wires and binding them together with an additional application of curable insulation. Although this is a workable method, the step of applying an additional coat of insulation requires some time for the insulated wires to be dipped into the curable insulating material, and then requires some time for that material to be cured. It would be advantageous to find some other way of binding a set of insulated wires together.